This invention pertains generally to defense systems for naval vessels and particularly to systems of such type which use radar-guided missiles to intercept and to destroy attacking air-craft or missiles and, in addition, may be used to detect and to track surface targets such as other naval vessels and navigational aids.
With the continued development of aircraft and missiles, along with more efficient tactics, a satisfactory solution to the problem of providing a dependable air defense system against air-craft and missiles has become more and more difficult to attain. In particular, when it is desired to provide a so-called xe2x80x9cpoint defensexe2x80x9d system for a naval vessel, it is now imperative that provision be made for the capability of modern aircraft and missiles to operate at high speed at very low altitudes. Further, it is imperative that such a defense system be effective when a naval vessel is under attack, either simultaneously or in rapid succession, by a number of aircraft or missiles. In such a situation, provision must be made in the air defense system to allow detection and tracking to be carried out effectively regardless of the number of attacking aircraft or missiles and the approach path of each such aircraft or missile.
As is very well known, uncontrollable interference effects (which almost invariably cause either, or both, a reduction in the range at which an airborne target may be detected or an error in the elevation angle of such a target) are experienced when a ship-borne radar is used to detect aircraft or missiles at low elevation angles over the sea. Therefore, one tactic which modern aircraft and missiles may easily and effectively follow is to attack while flying at very low altitude, where the effectiveness of any known radar-controlled point defense system is a minimum. It is, therefore, manifest that known radar guidance techniques may not always be successfully used and that improved radar guidance techniques, such as one using an active guidance system in an intercepting missile, must be used to attain the desired high degree of effectiveness.
Although the general principles underlying active radar guidance systems have been known for many years, the implementation of any such system in a practical air defense system for a naval vessel has heretofore posed the almost insuperable problem of providing a dependable, lightweight radar transmitter in a missile. The weight of electron discharge devices (along with the requisite high voltage supplies for such devices) and the fragility of electron discharge devices have made it impractical, except in special circumstances, to use any such device in a small missile suitable for the point defense mission.
It has been proposed to use solid state devices, such as IMPATT diodes, to generate the radio frequency energy required in the transmitter of a radar in an active guidance system in a missile. While such devices are light, dependable and require relatively small power supplies, their power outputs are extremely low. It is necessary, therefore, that the power outputs of many solid state devices be combined if a useful amount of radio frequency power is to be attained. While basic techniques for combining the radio frequency outputs of devices such as IMPATT diodes are well known, no technique has yet been developed which would allow efficient use of such devices in a pulse Doppler radar in a missile. In such an application, where pulse lengths may be in the nanosecond range, the known basic techniques (developed for continuous wave operation) referred to above are insufficient in themselves to overcome effects of transients and to provide pulses at predetermined frequencies.
Another basic difficulty in providing a point defense system for a naval vessel derives from the fact that the xe2x80x9creaction timexe2x80x9d (meaning the interval between detection of an attacking aircraft or missile and launch of an intercepting missile toward such aircraft or missile) of such a system must be extremely short to allow any possible threat to be met. A short reaction time makes it feasible to reduce the weights and sizes of the elements, such as the radar and the intercepting missiles, used in the system.
The factor limiting reaction time is the time taken actually to launch an intercepting missile on course to intercept. Unfortunately, conventional launching techniques (where intercepting missiles are mounted on launchers which are designed to be trained to align the intercepting missiles with the desired initial flight paths of such missiles) are too slow in operation and too heavy for smaller naval vessels. Further, known launchers cannot practicably be located to have an omnidirectional field of fire. This means that it is quite likely that a violent maneuver immediately after launch (when aerodynamic forces acting on the control surfaces of an intercepting missile are relatively weak) is needed to place an intercepting missile in the correct flight path toward an attacking missile. Any such maneuver is, of course, extremely wasteful of fuel and is, therefore, to be avoided if at all possible.
In view of the foregoing and other problems in the art as it now exists, it is a primary object of this invention to provide an improved point defense system for a naval vessel, such system utilizing an active radar-controlled missile and a radar adapted to detect and track a plurality of airborne targets, such as aircraft or missiles, whether such targets are at low or high altitudes.
Another object of this invention is to provide an improved point defense system for a naval vessel, such system having a short reaction time so that an intercepting missile may be launched within a few seconds after detection of an attacking aircraft or missile, thereby to overcome any tactical advantage attained by an attacking aircraft or missile during the initial stage of an engagement.
Another object of this invention is to provide an improved point air defense system for naval vessels of any size, such system being characterized by the fact that each one of the intercepting missiles used in such system is vertically launched before ignition of its rocket motor to provide an omnidirectional field of fire for all such missiles and, further, that initial maneuvering is effected, upon ignition of the rocket motor, by thrust vector vanes in the jet stream of the rocket motor.
Another object of this invention is to provide, in a system of the type contemplated herein, a capability to detect and track surface targets so that the system may be used to navigate a naval vessel in restricted waters or to detect and track friendly or hostile ships.
The objects of this invention are generally met in a defense system for a naval vessel by providing:
(a) a xe2x80x9ctrack-while-scanxe2x80x9d pulse radar, such radar emitting a beam which is mechanically scanned in azimuth and electronically scanned in elevation to allow a plurality of airborne or surface targets to be detected and tracked, the frequency of the pulses transmitted by such radar being varied in accordance with a predetermined program to reduce the deleterious effects of interference from the surface of the sea;
(b) a radar control unit, selectively responsive to command signals from an operator or to signals from the pulse radar, to cause-the scanning pattern of the beam from the pulse radar to be changed according to the tactical situation and the signals out of the receiver of the pulse radar to be processed to derive input signals for a control computer;
(c) a control computer programmed to respond to input signals from the pulse radar to differentiate between targets which pose a threat and other signals and to produce control signals which are effective either
(i) to effect tracking of any targets which pose a threat and to launch any one, or ones, of a number of missiles toward any such targets, or
(ii) to allow navigation of the naval vessel, and
(d) a number of missiles for launching, each one of such missiles being an active radar-guided missile which is vertically launched to have a short reaction time and which is adapted either to intercept an attacking aircraft or missile flying at any altitude above the sea or to be directed toward a surface vessel.